Plastic-based composite product and method and apparatus for manufacturing same

ABSTRACT

A plastic-based composite product comprising a plastic mass in which particles are homogeneously embedded, which particles have tensile strength in a first particle direction, the product having a chosen principal product direction, wherein the particles comprise: small particles being elongated plates of fibres and having a random orientation and a length of 0.2-2 mm; and large particles dominantly orientated such that their first particle direction is in the chosen principal product direction, the large particles having a length in the first particle direction of about 2-6 mm.

The invention relates to a plastic-based composite product whichconsists at least partially of a plastic in which a material consistingsubstantially of particles is homogeneously embedded, which particleshave tensile strength in at least one principal direction.

It is an object of the invention to provide a product which can bemanufactured at low cost but which nevertheless meets high standardswhich may be required in respect of diverse properties. Such propertiescan relate for instance to mechanical properties, fire resistance,weather resistance, non-ageing properties and the like.

With a view to the above, the invention provides a product of the statedtype which has the special feature that the particles comprise:

-   -   small particles, in particular plates or fibres with a random        orientation and a length of 0.2-2 mm; and    -   large particles with a dominant orientation, for instance        80-95%, of the said principal direction of the particles in a        chosen product principal direction and a length in the particle        principal direction of about 2-6 mm.

A specific embodiment has the characteristic that the large particlescomprise plates and the particle principal direction extends in the mainplane thereof.

In order to easily obtain the desired orientation of the plates theembodiment is recommended wherein the plates have an at least more orless isotropic tensile strength in their main plane.

Very suitable in this latter context is the variant wherein the platesconsist substantially of mica.

It is noted that according to the invention the particles can alsopossess a generally elongate form, whereby they may be designated asfibres.

A specific and very advantageous variant has the feature that theparticles consist predominantly of wood material and the plastic is athermoplastic polymer material, in particular at least one polyolefin orone polymer on a basis of styrene, wherein

-   -   a. the transverse dimension of the large wood particles is        preferably such that the ratio of the length in the principal        direction of the particles to this transverse dimension amounts        to a minimum of 4, but preferably lies in the range of 6-80.    -   b. the wood particles are present in a quantity of 40-80% by        mass, but preferably from 50 to 70% by mass in relation to the        mass of product.    -   c. the obtained product complies minimally with the following        requirements relating to mechanical properties in        -   bending strength in the fibre direction: 8 MPa        -   bending modulus in the fibre direction: 3 GPa        -   tensile strength in the fibre direction: 6 MPa        -   tensile stress modulus in fibre direction: 3 GPa        -   tensile strength transversely of fibre direction: 0.3 MPa        -   tensile stress modulus transversely of fibre direction: 1            GPa.

The invention herewith provides a product which in the manner to bedescribed hereinbelow can be manufactured on a basis of wood withoutwaste and, if desired, as a continuous process, which product not onlypossesses mechanical and physical/chemical properties corresponding withwood but which product can be manufactured on the basis of basic woodwhich can if desired be inferior and can be classified as interior wood,exterior wood or construction wood. This product according to theinvention will hereinafter be designated as technical wood.

The invention provides the possibility of applying the obtained productat locations where tropical hardwood is still indicated.

For this purpose particles with tensile strength such as wood particles,preferably originating from waste wood or wood waste, optionallytogether with suitable strengthening particles are predominatelyoriented and bound by means of a thermoplastic polymer, preferably on abasis of olefins or styrene, wherein the proportion of applied particlesis extreme relative to the binder polymer such that there is no questionof this being a fibre-filled thermoplastic material but an exceptionallywood-like material which, can be processed in a manner usual for anexpert.

It is important that the method can be performed continuously andcomprises the stages of compressing, compounding, fibre-orienting andshaping, wherein the following requirements must be fulfilled.

1. the compression stage wherein expulsion of included gases, bothinter- and intrafibular, must likewise take place under conditionswherein the fibres remain intact.

2. the compounding phase wherein the mixing of components and wettingwith polymer melt must take place under conditions wherein fibressensitive to breakage and splitting remain intact.

3. the orienting phase wherein a dominant orientation of long particlesin the compressed plastic material must take place under conditions suchthat the mutual position of the particles in the mix is by and largeretained, that is, the orientation proceeds along fluent flow lines,gradually and without such high shear stresses that there would therebybe a danger of thermal degradation.

4. the shaping phase wherein the mix acquires its fixed shape anddimensioning on the cross section perpendicularly of the flow direction,likewise under conditions wherein the relative mutual position of theparticles remains practically unchanged, for which purpose the materialflows under overpressure out of the mould head and remains at pressurein the calibrating unit until the binding polymer phase has cooled tobelow the Vicat softening temperature.

There is no extrusion here, since in extrusion the melted mass, afterleaving the extrusion head, is relatively pressureless or is at leastunder a relatively small overpressure such as is necessary to allow anafter-flow of the plastic core of the shaped product in the calibratingunit in order to thus enable replenishing of the material deficitresulting from shrinkage. This after-flow must always be avoided becauseit would be accompanied by delamination and a decrease in cohesionbetween particles and plastic and the desired properties wouldconsequently not be obtained.

There is also no question of pulltrusion since tensile forces aretherein exerted on the shaped product after and in the final part of theconsolidation phase for the purpose of continuous discharge of theshaped product, which otherwise acquires its shape in pressurelessmanner or under relatively small overpressure from a fusing ofthermoplastic and fibre reinforcement.

The method according to the invention involves a shaping process undercontinuous significant overpressure, wherein the material does not flowbut is pushed forward as a plastic plug through orientation, shaping andconsolidation phase.

This method is therefore designated with the name of pushtrusion.

The obtained product on the basis of wood particles and plastic,technical wood, is fully recyclable due to the fibre binding by means ofa thermoplastic. It will be apparent that recycled polyolefins andstyrenes can also be used as fibre binder.

Additives can moreover be added during the compounding phase, wherebyproperties are given to the technical wood which surpass those ofnatural wood, particularly when fast-growers such as firs, pines,birches and poplars are used as starting point.

The method as continuous process will be designated as compushtrusionand the apparatus in which the method is performed will be designatedcompushtruder.

Examples are known from the patent literature wherein plastic productsresembling wood are manufactured but wherein the mechanical propertiesas obtained according to the method of the invention are not obtainedtherein.

The known methods, insofar as a relatively high proportion of wood massis processed into the product, moreover make use without exception of amachine with a strong kneading action, such as for instance the Banburymixer or the Buss Co-kneader, which is deliberately not used in the newmethod in respect of the harmful effect of such a kneading machine onthe dimensions and properties of the applied wood fibres.

The applications of the products according to the known methods arelimited to ornamentation, covering, fence palings etc., wherein the woodpart is considered as filler:

-   -   EP-A-O 114 409, E.I. Du Pont de Nemours, 1994    -   U.S. Pat. No. 5,030,662, A. K. Banerjie, 1991    -   U.S. Pat. No. 4,866,110, Chang Y. Lee, 1989    -   U.S. Pat. No. 5,082,605, J. G. Brooks et aI, 1992    -   NL-A-77 04265, Lankhorst Touwfabrieken, 1978    -   WO-A-90/08020, Polywood Patent AB, 1990.        Description of the construction of the compushtruder

On the compushtruder can be distinguished:

-   -   (1) compounder: preferably twin-screw or single-screw with        adapted screw geometry,    -   (2) rotating displacement pump, preferably toothed wheel,        plunger or screw,    -   (3) distribution head    -   (4) orienting means,    -   (5) mould head, also calibrating device,        which parts are further described hereinafter.

(1) Compounder.

The function of the compounder, as for instance from the series TheysohnTSK-N, Leistritz ZSE-GL, is to encapsulate particles, in particular woodfibres, in the liquid thermoplastic. This must take place such that thewood fibre is completely enclosed with polymer, however, without thefibres effectively being shortened herein through breaking in thelength. The wood fibres may however split longitudinally. This situationis achieved by the polymer melt wetting the fibres. Due to therelatively strong adhesion properties of the melt in relation to thefibres the latter are carried along and dispersed homogeneously furtheron in the melt phase. Adapting the screw geometry prevents too intensivea kneading action being applied to the mixture, as is usually the casewith, for instance, the Banbury mixer or a standard compounder. Aconscious choice has been made for a long compounding path instead of ashort sharp one, wherein the wood particles are handled carefully whilea homogeneous dispersion nevertheless occurs. The wood particles arepreferably introduced under compression and compacted to prevent excessair inclusion which could affect the quality of the end product.

By successively compressing, decompressing and degassing under vacuumthe mixtures by means of the chosen screw geometry, air and gases areexpelled, both from the mixture and from the pores in the fibres. In thecase of a single-screw compounder, the mixture is driven in a compressedplug flow, whereafter the thermoplastic part is melted.

The adhesion between wood particles and polymer melt is so great andadheres such that optional further additions can be made to the mixturewithout breaking the adhesion between polymer and wood particles.

Optional reinforcing fibres on a basis of cellulose, such as flax, hempor mlneral fibres or glass, (mica) plates or the like can be carriedalong in the above path.

The pressure on the mixture for the purpose of the shaping phase is notprovided, as is usual, by the principle of the extruding action of thescrew but by a rotating displacement pump interposed for this purpose.

(2) Rotating Displacement Pump

The pressure required to press the mixture through the distribution head(to be described below), the orienting means and the mouldhead/calibrating device is produced by a displacement pump, preferably ascrew pump of a gear pump, for example Maag, Expac type Extrrex 56/56 orWitte type ESTHF 92.6LKK. High pressures can be realized without anysignificant effect on particle shape and dimensions. Moreover, sincelarge shearing forces are practically absent, the desired pressureincrease can be realized without excessive thermal load and degradationof the mixture.

(3) Distribution Head

The distribution head is a necessary “interface” between rotatingdisplacement pump and orienting means. The laminar flow pattern from therotating displacement pump must be converted to a plug flow.

The particle orienting means must be supplied with a constant flow ofmixture which in quantity and speed is distributed equally over the flowsurface of the orienting means, this in order to prevent blockage andturbulence as result of speed differences after each phase of theparticle orientation. The distribution head thus initiates the requiredplacidity within the flow profile, The plug flow can be optimalized:

-   -   mechanically by varying the through-flow surface per channel        using adjustment bolts which can be accessed from outside and/or    -   thermally by varying the flow resistance per channel using        heating elements.

The form of the distribution head depends partly or wholly on thedesired product.

(4) Orienting Means.

The orienting means consist of a plurality of plates connected in serieswith slits (in the case of plates) or (cylindrical) holes (in the caseof fibres) in the flow direction. The total through-flow surface perplate is mutually equal. The diameter of the holes decreases over theplates connected in series. The diameter and the decrease thereof overthe plates depends on the particle dimensions and the desired degree oforientation. When short fibres with a length of 2 mm and an L/D ratio of4 are guided through a hole of 2.5 mm, little or no orientation willoccur.

If a long fibre with a length of 4 mm and an LID ratio of 8 passesthrough the same hole, then orientation will occur.

The number of plates depends on the degree of uniformity in the fibrelength, the LLD ratios thereof and the desired degree of orientation.

The length of the slits or cylindrical hole is preferably at least equalto the maximum linear particle dimension.

Transition plates between the hole plates with different diameters haveof course the same through-flow surface as the hole plates.

(5) Mould Head/Calibrating Device

In order to make a two-dimensionally shaped endless product from the“wood mixture” with the oriented particles a mould head and acalibrating device are necessary. In contrast to the typically usedextrusion shaping process, mould head and calibrating device areconstructed integrally in the compushtrusion process, since thepushtrudate may not be pulled or have pressure exerted thereon inlengthwise direction.

An essential condition for obtaining technical wood is that aftershaping the mixture is cooled under pressure to below the Vicatsoftening temperature of the binder thermoplastic. This consolidationprocess is necessary to prevent delamination and matrix failure.

The system pressure is derived from the flow resistance between mixtureand mould head/calibration.

In order to prevent delamination and matrix failure in the calibrationthe first part hereof is covered with a coating which substantiallyreduces the surface resistance to a value wherein no delamination andmatrix failure occurs. The outer part of the product meanwhile cooled tobelow the Vicat softening temperature in the calibration provides matrixsupport of that part of the product, the material core, still lyingbelow the Vicat softening temperature.

Process Parameters

It will be apparent that in the compushtrusion process many parameterscan be distinguished which all have their influence on the creation,quality and properties of the technical wood.

The process parameters can be sub-divided as follows:

-   -   (1) Variable parameters, being adjustable parameters which can        be varied on-line.    -   (2) Adaptable parameters are set once, subject to the type of        technical wood and the desired product section.        Variable Parameters

(1) The variable parameters can be further sub-divided into twocategories:

-   -   a. as they also occur in the known compounding/extrusion        process:        -   temperatures, for instance set temperature profile of the            screw cylinder, temperature of mould head,        -   screw rotation speed,        -   with twin-screw compounder: the filling level by means of            dosaging,        -   pressure, interactive,        -   degassing, absolute pressure of the vacuum.    -   b. new compushtrusion parameters:        -   through-flow surface adjusted by means of adjustment bolts            and/or temperature profile of the channels in the            distribution head,        -   temperature of the particle orienting provision, temperature            of the calibration,        -   rotating displacement pump temperature,        -   rotating displacement pump pressure and output.    -   (2) Adaptable parameters        -   screw geometry,        -   manner and position of dosage,        -   degassing zones and number,        -   L/D ratio of the compushtruder,        -   number of orientation plates,        -   diameters and lengthwise change in the holes in the            orientation plates,        -   flow resistance in the mould head/calibrating device,        -   position and active length of the resistance        -   reducing coating in the calibrating device.            Example of the method and the mechanical properties of            obtained technical wood.

The method is performed in a compushtruder as described above with acapacity of 200 kg per hour.

The composition of the mixture is as follows:

-   -   60% by mass pinewood, length of the fibrous particles 0.6-3 mm,    -   L/D=4, moisture content 2.2% by mass    -   40% by mass polypropylene. MFI=15 dg/min, (230/2,16)    -   no other additions.

The most important process parameters are as follows:

-   -   temperature profile in the range 160-195° C.    -   compounder feed pressure 15 bar    -   rotating displacement pump pressure 95 bar    -   vacuum 20 kPa.        Measured Mechanical Properties of the Technical Wood:

Six samples were measured wherein the following results were obtained inrespect of the length orientation of the wood particles: Tensilestrength tests (ISO 527) standard deviation Maximum tensile force 23.5MPa 0.4 MPa E-modulus 5.737 GPa 0.104 GPa Tensile strength 12.2 MPa 0.35MPa transversely of fibre direction Tensile stress modulus 2.122 GPA0.102 GPa transversely of fibre direction Bendinq tests (ISO 178):Maximum bending load 32.0 MPa 0.3 MPa Bending modulus 3.849 GPa 0.098GPa

Addition of 10% glass or flax fibre with a length of 4 mm and L/D 150 to400 gives values about 25% higher than shown above.

A product can in principle be manufactured in any suitable manner,starting from pre-compounded material or semi-manufacture, for instanceby (isostatic) pressing, injection moulding, extruding, compushtruding.

A specific embodiment has the feature that the product consistssubstantially of a laminate comprising a plastic-based composite layeraccording to the above stated specifications; a first skin layer adheredthereto on one side and possessing chosen properties; optionally asecond skin layer adhered thereto on the other side and possessingchosen properties; and which layers are mutually adhered by for instancegluing, welding, mirror-welding, with an infrared laser, with hot air orother suitable treatment.

Another embodiment is characterized by at least one additive forobtaining desired properties, which additive is added to the processflow at a suitable position in the compushtruding process duringmanufacture of the product.

The said chosen properties of the skin layers may relate for instance tothe adherability of paint, lacquer and glue.

A variant of this latter embodiment has the feature that the skin layeror at least one of the skin layers is of the type according to theinvention and the long particle orientation thereof has a chosendirection relative to this orientation of the first mentioned plasticlayer. Specific mechanical properties can hereby be achieved. These canbe based for instance on the Stringer effect.

As already noted, the product according to the invention lends itselfvery well for manufacture by means of a process which can best bedescribed as compushtrusion. In this respect the invention likewiseprovides a compushtrusion apparatus for manufacturing a product of theabove specified type, which apparatus comprises: a compounder operatingat low pressure for plasticizing a mixture consisting substantially ofplastic and particles with tensile strength, which particles are mixedwith the plastic either beforehand or in the compounder, and pressingthe plastic mixture to the outside via an outlet;

-   -   a rotating displacement pump further transporting the plastic        mixture;    -   a distribution head further guiding the mixture in order to        further transport the plastic mixture substantially as a plug        flow;    -   orienting means further guiding the mixture, comprising at least        one bundle of substantially parallel channels through which the        plastic mixture can flow and which are dimensioned relative to        the long particles such that, other than to a dominating extent        in the particle principal direction, they are too small to allow        passage of the long particles present in the plastic mixture;        and    -   a substantially prismatic mould head which connects onto the        outlets of the channels and the form of which corresponds with        the desired cross sectional form of the product;    -   such that the principal direction of the particles corresponds        with the longitudinal direction of the mould head and the        principal direction of the product;    -   which mould head is so long and has a temperature curve in the        longitudinal direction such that at the end of the mouth the        product has cooled to below its Vicat softening temperature.

As already discussed, the adhesion of lacquer, paint and glue can beenhanced by mechanical means, for instance due to a certain porosity andprotruding fibres. Another embodiment which achieves the same effect inchemo-physical manner is characterized by an additive with a desiredinfluence on chosen properties of the product and belonging to at leastone of the following classes:

-   -   influencers of adhesion between particles with tensile strength        and matrix polymerr (class H),    -   influencers of the properties of the surface of the product,        particularly in respect of coatings or adhesives for applying in        sandwich structures (class 0),    -   influencers of the pyrogenic properties (class P),    -   influencers of the particle durability (class D),    -   blowing means for obtaining a foamed structure (class B), in the        case of a sufficiently high temperature increase.

The invention will now be elucidated with reference to the annexeddrawings, wherein:

FIG. 1 shows a highly schematic, partly broken away perspective sideview of a compushtrusion apparatus with which a product according to theinvention can be manufactured;

FIG. 2 shows a highly schematic side view of an apparatus with whichanother product according to the invention can be manufactured;

FIG. 3 is a cut away perspective view corresponding with FIG. 1 of avariant; and

FIG. 4 is a cut away perspective view on enlarged scale of a part of theapparatus according to FIG. 3.

FIG. 1 shows a compushtruder 1. This comprises a compounder 2, arotating displacement pump 3, a distribution head 4, a particleorienting member 42 and a mould head/calibrating unit 43. Thedistribution head 4 and the orienting head 5 comprise continuouschannels through which can pass the plasticized plastic, in which fibreswith tensile strength are incorporated. The long fibres have a lengthpredominantly in the range of 2-6 mm. In order to give these fibres thedesired orientation, that is, the longitudinal direction designated witharrow 6, the continuous channels comprise in the distribution head 4 andthe orienting head 5 sub-channels having an effective diameter of forinstance in the order of 6-8 mm, taking account of the wish to choosethe diameter size of the said channels such that the orientation of theshort fibres in not affected. It will be apparent that for other fibrelengths the said passages can be adapted correspondingly. The product 7consists substantially of the solidified composite mass in which thelong fibres extend generally at least roughly in longitudinal direction6.

FIG. 2 shows an alternative. Two compushtruders 8, 9 deliver products10, 11 respectively in the direction of the pinch between two rollers12, 13. At the position of the pinch 14 a plastic-impregnated fibre mat15, comprising for instance glass or aramide fibres, is introducedbetween the plate-like products 10, 11 by transport rollers 16, 17. Alaminate 18 is thus formed by heating and by the force exerted byrollers 12, 13. The fibres in the fibre mat 15 extend substantially inthe longitudinal direction 6. At least one of the products 10, 11displays a desired porosity in order to ensure properties correspondingwith wood.

For greater thicknesses a product can be manufactured from a pluralityof laminates placed one on top of another and mutually adhered by athermal treatment and pressure.

It is further noted in general that binders can also be added to thebasic plastic in order to improve the adhesion between fibres, plasticand other additives. The adhesion to the product according to theinvention of paints and lacquers on acryl-water basis can hereby alsoimprove.

The use of colouring agents or pigments in the mass can provide theadvantage that a uniform product is obtained.

With reference to FIG. 2 attention is drawn to the fact that by makinguse of for example co-extrusion or other suitable technique on theproduct according to the invention an additional coating can be appliedto the visual side of the product. Such a coating can have anextra-stable colour, an increased UV-resistance or resistance to dirtand weather influences.

In contrast to the above mentioned prior art the invention provides aproduct which lends itself for processing and treating as wood. Thefollowing considerations are paramount here.

The product according to the invention can have a linear expansionsimilar to wood and also has a similar strength and stiffness with acomparatively great toughness and excellent cracking strength. Theproduct can display fire characteristics which, by making use ofenvironmentally-friendly provisions, must be at least the equal of thefire characteristics of normal wood and which when it burns may notproduce any more smoke and harmful substances than normal wood. At aspecific weight of 750-1250 kg/m³, the process and the required rawmaterials and additives may not exceed the price of normally processedwood.

In terms of appearance and weight the product according to the inventioncan if desired display a striking similarity with natural wood ortraditionally pressed wood such as MDF or wood fibre board.

The product according to the invention can be worked with normal toolsand normal wood processing machines. In the usual manner of wood it canbe nailed, sawn, screwed, glued, painted and lacquered.

The product according to the invention can possess an excellentresistance to climatological conditions such as moisture, sunlight withultraviolet component, temperature changes etc.

The products according to the invention are better suitable forrecycling after use than natural wood.

The products according to the invention are superior to wood in respectof moisture absorption, rotting, swelling and the like.

FIG. 3 shows a compushtruder 21 which has a structure differingpartially from that drawn in FIG. 1. A distribution head 23 connectsonto the rotating displacement pump 3 (see also FIG. 4). This block hasa more or less conically tapering inlet space 24 which debouches into afan of nine channels 25-33. FIG. 4 in particular shows clearly theinternal structure of the distribution head 23. By means of screwscontrollable from outside, which are all designated 34 for the sake ofconvenience, the effective passage and therewith the flow resistance ofchannels 25-33 can be individually adjusted. An excellent homogeneity ofthe through-flowing mixture can hereby be ensured. Alternatively, theeffective through-flow of the channels can be influenced by a selectiveheating. The through-flow of a channel can in any case be improved byreducing the flow resistance. This can be achieved not only by adjustingthe passage but also by changing the temperature, whereby the viscosityof the through-flowing mixture changes, at least in the boundarysurface, thereby changing the effective through-flow.

Via a collection space 35 the plastic mixture allowed through is fed toa bundle 36 of channels which is bounded by plates extending one on topof another in transverse direction. By means of channels 37 sufficientheat can be supplied to the through-flowing mixture to keep it inplastic state. A second bundle 38 follows the first bundle 36 via aninterspace 37. A third bundle 40 follows via an interspace 39.

Downstream of this latter bundle 40 is situated the mould head 41 of thecompushtruder 21. By means of calibrating and cooling means the productis then cooled gradually while a sufficient pressure is maintained, andis carried to the outside in the correct dimensions. Product 42according to FIG. 3 has an orientation of the long fibres correspondingwith the mould longitudinal direction.

The diameters of the mutually adjacent round channels in bundles 36, 38,40 amount in this embodiment to respectively 14 mm, 8 mm and 6 mm whileretaining the same through-flow surface.

It will be apparent from the structure shown in FIG. 4 that the massflowing through the more inwardly located channels has a smaller flowresistance than the mass flowing through the more outwardly locatedchannels, since they are longer. In this context the more inwardlylocated channels can have a slightly smaller diameter.

It is noted that in all compushtruders the mixture with the fibresembedded therein is introduced into the mould head by the rotatingdisplacement pump at a relatively high temperature above the Vicatsoftening temperature, for instance 180° C., cools during the transportthrough the mould head and has reached a reduced temperature at the endsuch that the exiting product has a temperature below the Vicatsoftening temperature, whereby it is sufficiently cured that it will nolonger undergo any substantial change in shape.

1. Plastic-based composite product which is comprised least partially ofa plastic having a plurality of particles homogeneously embedded in saidplastic, which particles have tensile strength in at least one principaldirection. said plurality of particles comprising: small particles, inthe form of plates or fibres with a random orientation and a length of0.2-2 mm, and large particles with a dominant orientation, of the saidprincipal direction of the particles in a chosen product principaldirection and a length in the particle principal direction of about 2-6mm.
 2. Product as claimed in claim 1, characterized in that the largeparticles are plates and the particle principal direction extends in themain plane thereof.
 3. Product as claimed in claim 2, characterized inthat the plates have an at least more or less isotropic tensile strengthin their main plane.
 4. Product as claimed in claim 3, characterized inthat the plates consist substantially of mica.
 5. Product as claimed inclaim 1, characterized in that the large particles are fibres whereinthe principal direction of the particles is the longitudinal directionof each fibre.
 6. Product as claimed in claim 1, characterized in thatthe particles consist predominantly of wood material and the plastic isa thermoplastic polymer material, wherein a. the transverse dimension ofthe large wood particles is such that the ratio between the length inthe principal direction of the particles and this transverse dimensionamounts to a minimum of
 4. b. the wood particles are present in aquantity of 40-80% by mass, in relation to the mass of product. c. theobtained product complies minimally with the following requirementsrelating to mechanical properties in bending strength in the fibredirection: 8 MPa bending modulus in the fibre direction: 3 GPa tensilestrength in the fibre direction: 6 MPa tensile stress modulus in fibredirection: 3 GPa tensile strength transversely of fibre direction: 0.3MPa tensile stress modulus transversely of fibre direction: 1 GPa. 7.Product as claimed in claim 6, characterized in that the wood particlesoriginate from softwood or hardwood.
 8. Product as claimed in claim 6,characterized in that other particles with tensile strength are presentin an amount of 3-25% by mass.
 9. Product as claimed in claim 8,characterized in that other particles with tensile strength are presentwhich originate from at least one type of from the class of inorganicpolymers on a basis of silicates.
 10. Product as claimed in claim 8,characterized in that other fibres with tensile strength are presentconsisting of glass fibres, chopped strands with a length of 4-5 mm anda diameter of 0.013 mm and a ratio of length to diameter in the range of300-400.
 11. Product as claimed in claim 8, characterized in that otherfibres with tensile strength are present which are at least one of theclass of the natural biopolymers on a basis of cellulose, wherein thepercentage of said natural biopolymers present depends on the number ofexternal appendages on the fibres.
 12. Product as claimed in claim 6,characterized in that the polymer material consists of polypropylene,polystyrene, polyethylene or polyacrylate.
 13. Product as claimed inclaim 12, characterized in that the polymer material consists of one ormore olefinic homo-or copolymerisates with an H.F.I. (230/2,16) of 1-30dg/min; and which polymeric matrix material forms 10-50% by mass of thewood.
 14. Product as claimed in claim 1, characterized by at least oneadditive for obtaining desired properties, which additive is added tothe process flow at a suitable position in the compushtruding processduring manufacture of the product.
 15. Product as claimed in claim 14,characterized by an additive with a desired influence on chosenproperties of the product and belonging to at least one of the followingclasses: influencers of adhesion between particles with tensile strengthand matrix poly (class H), influencers of the properties of the surfaceof the product, particularly in respect of coatings or adhesives forapplying in sandwich structures (class 0), influencers of the pyrogenicproperties (class F), influencers of the particle durability (class D),blowing means for obtaining a foamed structure (class B), in the case ofan unintended, sufficiently great temperature increase.
 16. Product asclaimed in claim 14, characterized in that as additives with a positiveinfluence on the desired properties of the technical wood one or more ofthe following are present therein indicating the class or classes andthe applied percentage related to the mass of technical wood: AdditiveClass Mass-percentage Polybond (Spider) H 0   1-3, Polyweb (DOW) H 0  1-3, Exxelor (Exxon) H 0   1-3, tributoxyethylphosphate H O P   1-5,1,2,3-propane trial H 0 V   2-3 diamrnoniumphosphate P D   2-8ammoniumcarbonate P B   1-3 amrnoniumhydrogencarbonate P B 1,2-ethanediol 0 D up to 3 ethylacetate/ethanol ½-⅓ 0 up to 3 methyl acetate H 0up to 4 n-propanol 0 up to 1.5 silane A 171, 172, 174 H O D 0.5-3polyvinyl acetate H O D up to 5 surfactants, ionogenic/ H 0 up to 2aniogenic, standard chlorinated polyolefins H 0 up to 5 UV-stabilizers Dup to 3 azodicarbonamide P B up to 3


17. Product as claimed in claim 1, characterized in that at least onecolouring agent or pigment is added to the product during manufacture.18. Product as claimed in claim 1, characterized in that the productcomprises: a plastic-based composite layer a first skin layer adheredthereto on a first side thereof optionally a second skin layer adheredthereto on a second side thereof; and which layers are mutually adhered.19. Product as claimed in claim 18, characterized in that at least oneskin layer is of the type as claimed in claim 1 and the productprincipal direction thereof has a chosen direction relative to thisproduct principal direction of the first mentioned plastic-basedcomposite layer.
 20. Apparatus for manufacturing a product as claimed inclaim 1 comprising: a compounder operating at low pressure forplasticizing a mixture of plastic and particles with tensile strength,which particles are mixed with the plastic either beforehand or in thecompounder, and pressing the plastic mixture to the outside via anoutlet; a rotating displacement pump further transporting the plasticmixture; a distribution head further guiding the mixture in order tofurther transport the plastic mixture substantially as a plug flow;orienting means further guiding the mixture, comprising at least onebundle of substantially parallel channels through which the plasticmixture can flow, which channels are dimensioned relative to the longparticles such that, other than to a dominating extent in the particleprincipal direction, said channels being too small to allow passage ofthe long particles present in the plastic mixture; and a substantiallyprismatic mould head which connects onto outlets of the channels, saidoutlets having a form which corresponds with a desired cross sectionalform of the product; such that the particle principal directioncorresponds with the longitudinal direction of the mould head and theproduct principal direction; which mould head is so long and has atemperature curve in the longitudinal direction such that at the end ofthe mouth the product has cooled to below its Vicat softeningtemperature.
 21. Apparatus as claimed in claim 20, wherein the lineartransverse dimensions of at least the parts of the channels locatedfurthest downstream amount to a minimum of 2× the length of the shortfibres and a maximum of 1.5× the length of the long fibres. 22.Apparatus as claimed in claim 20, comprising at least two bundles ofchannels mutually connecting in series, wherein the transversedimensions of the channels of a bundle located further downstream aresmaller than those of the channels of a bundle located further upstream.23. Apparatus as claimed in claim 20, wherein the effective passages ofthe channels of the distribution head are adjustable.
 24. Apparatus asclaimed in claim 20, wherein at least one feed for adding particlematerial and/or additives to the plastic connects to the compounder. 25.Apparatus as claimed in claim 20, further comprising particle supplymeans which are adapted to introduce the particles into the compounderunder a pressure such that these are compressed while air is expelled.26. Apparatus as claimed in claim 25, further comprising compressionmeans for compressing the particle material to expel gases prior toaddition of the plastic.
 27. Apparatus as claimed in claim 20 whereinthe compounder has a screw with a geometry such that the plastic mixturein which the particles are incorporated is successively compressed,decompressed and degassed under vacuum such that air and other gases areexpelled from the mixture and from the pores present in the particles.28. Method for manufacturing a product as claimed in claim 1characterized in that the finished product is subjected to anafter-treatment comprising heating the product to a temperature abovethe Vicat softening temperature of the applied plastic respectively thehighest Vicat softening temperature of all the applied plastics,modelling the product to a desired shape and while maintaining a chosenpressure causing the product to cool in this shape to below the saidVicat softening temperature.
 29. Product obtained with the method asclaimed in claim
 28. 30. Method for manufacturing a product as claimedin claim 12, characterized in that as starting polymer material is useda prepolymer on the basis of a styrene or an acrylate.
 31. Product asset forth in claim 6 wherein said polymer is at least one polyolefin orpolymer based on styrene.
 32. Product as set forth in claim 6 whereinthe ratio between the length in the principal direction of the particlesand the transverse dimension is in the range of 6 to
 80. 33. Product asset forth in claim 6 wherein the wood particles are present in aquantity of 50 to 70% by mass in relation to the mass of the product.34. Product as set forth in claim 7 wherein said wood particlesoriginate from at least one of fir, spruce, birch or poplar.
 35. Productas set forth in claim 8 wherein other particles are present in 5 to 18%by mass.
 36. Product as set forth in claim 9 wherein said otherparticles are glass.
 37. Product as set forth in claim 11 wherein thenatural biopolymer is a member selected from the group consisting offlax, jute, hemp, sisal, coconut, bamboo and miscanthus.
 38. Product asset forth in claim 13 wherein said H.F.I. is 2-15 dg/min.
 39. Product asset forth in claim 13 wherein said polymeric matrix forms 15-40% by massof the wood.